feat: Implement NewRouter function for serving frontend static files

backend/internal/server/server.go

@@ -0,0 +1,21 @@
+package server
+
+import (
+	"github.com/gin-gonic/gin"
+)
+
+// NewRouter creates a new Gin router with frontend static file serving.
+func NewRouter(frontendDir string) *gin.Engine {
+	router := gin.Default()
+
+	// Serve frontend static files
+	if frontendDir != "" {
+		router.Static("/assets", frontendDir+"/assets")
+		router.StaticFile("/", frontendDir+"/index.html")
+		router.NoRoute(func(c *gin.Context) {
+			c.File(frontendDir + "/index.html")
+		})
+	}
+
+	return router
+}